Video playback systems typically work with compressed video. Compression of a video can be done using a variety of different codes, and corresponding codecs compress the video by removing redundant information from frames of the video such that the redundant information may be reconstructed when the frames are displayed. Many codecs use I-, P-, and B-frames. An I-frame is decoded without reference to another frame, a P-frame is decoded with reference to one or more frames that are displayed before the P-frame, and a B-frame is decoded with reference to one or more frames that are displayed after the B-frame and zero or more frames that are displayed before the B-frame. In playback of an I-P-B video, the video playback system typically decodes frames in a decode order that is different from the display order, typically due to dependencies of B-frames. In other words, before a B-frame may be decoded, all frames upon which the B-frame depends are decoded. Consequently a frame that is displayed after the B-frame may be decoded before the B-frame.
When testing a video system supporting frame-reordering codecs, it can be difficult to visually identify whether the correct sequence of prediction frames was decoded. For example, errors may occur in the identification of the decode order, because the decode order differs from the display order. Such errors result in incorrect decompression of the frames of the video, because the frames are decoded based on incorrect dependencies that are indicated by the incorrect decode order. Decompression errors may be hard to detect, because an incorrectly decompressed frame may be displayed for only a short amount of time. Furthermore, the cause of the incorrect decompression may be hard to identify even if one determines that a frame was displayed incorrectly. More particularly, the incorrect dependencies for the frame, and the corresponding incorrect decode order, may be hard to identify based only on an indication that the frame has been displayed incorrectly.